A characteristic-line x-ray source is proposed for dual-energy subtraction imaging of small areal densities of iodine in the human coronary arteries. The source is based on the production of the K-alpha, lines in a rotating metal compound target bombarded by a high energy electron beam. In Phase 1, x-ray spectra from various target configurations were calculated using a Monte-Carlo electron-photon code and a dual-energy imaging simulation code was developed to calculate image signal-to-noise ratio for a range of iodine and tissue parameters. The calculations indicate that an optimized system would be capable of imaging 2 mg/sqr. cm of iodine contrast agent in 20 g/sqr. cm of tissue with a SNR=5 and a total imaging time of 10 ms. In addition, the cost and size of the x-ray source designed in Phase I are compatible with clinical use. In Phase II, proof-of-principle experiments will be performed to verify the operating capabilities and constraints of the proposed x-ray source. A prototype electron accelerator and target assembly will be constructed and used to conduct dual-energy subtraction imaging experiments on phantoms. Two detector configurations will be evaluated. An upgraded accelerator and target design capable of providing the high photon fluxes required for the clinical implementation of this technique will be developed.